One important consideration in manufacturing pharmaceutical packages or other vessels for storing or other contact with fluids, for example vials and pre-filled syringes, is that the contents of the pharmaceutical package or other vessel desirably will have a substantial shelf life. During this shelf life, it is important to isolate the material filling the pharmaceutical package or other vessel from the vessel wall containing it, or from barrier layers or other functional layers applied to the pharmaceutical package or other vessel wall to avoid leaching material from the pharmaceutical package or other vessel wall, barrier layer, or other functional layers into the prefilled contents or vice versa.
Some companies have turned to plastic pharmaceutical packages or other vessels, which provide greater dimensional tolerance and less breakage than glass, but its use for primary pharmaceutical packaging remains limited due to its gas (oxygen) permeability: Plastic allows small molecule gases to permeate into (or out of) the article. The permeability of plastics to gases is significantly greater than that of glass and, in many cases (as with oxygen-sensitive drugs such as epinephrine), plastics have been unacceptable for that reason.
The problem of permeability has been addressed by adding a barrier coating or layer to the plastic pharmaceutical package where it contacts fluid contents of the package. One such barrier layer is a very thin coating of SiOx, as defined below, applied by plasma enhanced chemical vapor deposition. But, current SiOx barrier layers deposited on a package by PECVD are etched off by aqueous contents of the package having pH-values greater than 4, particularly at higher pH values. This reduces the useful shelf life of the package as its barrier efficacy is reduced.